The objective of this research is to gain information about the mechanical properties of the cochlea in order to understand the inert structures before moving to more complicated representations. This information will guide in the creation of models, whose ultimate objective is to explain the mechanical process used for receptor cell stimulation. The first specific aim is to measure the variation of basilar membrane stiffness in the longitudinal direction. This is the most important parameter in the phenomenon of traveling waves with frequency-dependent maxima. The only data available currently is that of G. von Bekesy, but its applicability to the in vivo state is doubtful. For example, investigators have found that a compliance one-fourth as large gives results that agree better with experiments. An accurate measure is surely needed for a basis on which to judge the suitability of mathematical models. The procedure for this will follow one already used successfully to determine the radial variation of basilar membrane compliance. The second aim is to obtain mechanical properties of the micromechanical elements of the cochlea and surrounding structures. Such properties are presently guessed or approximated in three-dimensional cochlear models containing details of the partition and organ of Corti. Both static and dynamic measurements of the tectorial membrane, primary osseous lamina, hair cells, and entire arch structure will be made. Using well-known mechanical representations, this data will be used to obtain basic properties including Young's modulus, shear modulus, viscoelastic moduli, and type of attachment to surrounding tissue. The results will then indicate the important features in the overall response, allowing prediction of how the cochlea will behave when certain elements are diseased and what the effect of cochlear prostheses will be.